On our  THS, I have noticed on several occasions (not just my pair of lanes), that you will hit the pocket really well and actually see a pin or pins get hit and just slide.  Sometimes just a bit, and sometimes can slide to a different position completely, ie: 5 pin slides to 8 spot.  Again, this does not always happen, maybe once every 4-8 weeks.  Our shot is 41', and as far as I know stripped first, I see when the machine oils, that it goes right through the deck  clears the pins.  At this point, is the machine buffing out oil, or is it just residue oil left on the deck from the bottom of machine?  I do know this last time it happened, there was a 6 game tourney the day before on the shark pattern, that may have had something to do with it.  I will say, when this happens, you see some really weird stuff/leaves happen.  Is this the machine setting or a  malfunction?  Just curious.